This invention relates to an image data transmission system for use in combination with a craft, such as a spacecraft, an aircraft, or the like, flying over an object zone which may be a ground surface of the earth or the like.
An image data transmission system of the type described, comprises an image pickup system for sensing the object zone on board a craft flying over the object zone along a flight path. A recent requirement is to provide a topographic or a like image at a high resolution so as to get a precise topography or the like. This requirement gives rise to an increase of a succession of image signals picked up on board the craft. Such an image data transmission system is therefore in need of data compression process. As a typical one of such data compression processes, a predictive encoding unit is well known. As will later be described with reference to a few figures of the accompanying drawing, a conventional predictive encoding unit is hard to follow a drastic amplitude variation of image signals.